what is the formula used to get the answer?

Department X of a manufacturing company works on only one product, and all costs are incurred uniformly as the product goes along the assembly line. The 12,000 units in process on December 1 were 60% completed. An additional 38,000 units were placed in production during December. On December 31, the 22,000 units in process were 56% completed. The equivalent units of production during December amounted to